I'm down to the amplifer and can't get the wiring harness to unplug. Is the a secret to unplugging it?

 

There is a plastic tab at the middle of each connector. Squeeze the connector so the tab is flush. Then pull smoothly. The connectors can be sticky and reluctant to come out. Squeeze the tab harder and pull smoothly. When you get them out, add a bit of grease to the contacts and the outside of the housing. They will be easy to get out from then on.